1. Field
This disclosure relates generally to amplifiers, and more specifically, to amplifiers having an active inductor.
2. Related Art
Systems that have circuits that are operating at especially high frequencies raise problems that arise due to the high frequency. For example, when a signal has to traverse a distance, parasitic capacitance increases as the distance increases. The parasitic capacitance acts as a low pass filter so that as the distance increases the high frequency is attenuated more and more. Another adverse effect of high frequency is what is called the “skin effect.” As the frequency increases the current is conducted more and more along the surface of the conductor. With less of the conductor carrying current, the resistance increases for a given conductor as the frequency increases. Thus, the inherent low pass filter arising from the series resistance increase and the parasitic adversely impacts the ability to operate at higher frequencies.
To offset the low pass filter, a high pass filter may be introduced. One approach is to use an inductor, passive or active, that can offset the effects of the low pass filter. Passive inductors can require a significant amount of space on an integrated circuit and thus add significant cost. Depending on the particular type of passive inductor, the inductance can be difficult to control. Active inductors also tend to be difficult to control.
Accordingly there is a need for an amplifier to offset the adverse effects of high frequency operation in a manner that overcomes or improves upon the issues raised above.